Diffraction-type surface-emitting semiconductor laser and method for manufacturing the same

Abstract

The present application provides a diffractive surface-emitting semiconductor laser and a preparation method thereof. The diffractive surface-emitting semiconductor laser includes an active layer and a complementary optical modulation layer in one or more of the upper cladding layer, the upper waveguide layer, the lower waveguide layer, and the lower cladding layer. The complementary optical modulation layer includes an upper optical modulation layer and a lower optical modulation layer. The lower optical modulation layer has a first optical modulation material and a second optical modulation material with different refractive indexes, and these two types of optical modulation materials form a high and low refractive index difference. The upper optical modulation layer has a third optical modulation material and a fourth optical modulation material with different refractive indexes, and these two types of optical modulation materials form a high and low refractive index difference. In the direction perpendicular to the laser output surface, the region where the second optical modulation material is located corresponds to the region where the fourth optical modulation material is located, and the region where the first optical modulation material is located corresponds to the region where the third optical modulation material is located.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor lasers, and particularly to a diffractive surface-emitting semiconductor laser and a preparation method thereof. Background Art

[0002] In 2022, Kyoto University in Japan released a technical route for realizing high-power single-mode output of a photonic crystal surface-emitting laser (PCSEL) (Literature 1). The following year, they reported a PCSEL with a continuous output power of 50 W, a divergence angle of less than 0.05°, and a brightness of 1 GW / cm 2 ·sr. The PCSEL belongs to a horizontal cavity surface-emitting structure and uses a planar waveguide structure, enabling the optical field to be in the fundamental mode in the z direction. A photonic crystal structure is fabricated in the cladding, and the diffraction effect of the second-order grating is utilized to generate a diffraction component in the z direction to achieve surface emission. Similarly, surface emission can also be achieved by replacing the photonic crystal with an annular grating, except that there are differences in the optical field distributions between the two. In 1990, Dr. Toda conducted theoretical calculations for a disk-shaped DFB laser. Dr. P. L. Greene and Professor D. G. Hall at the University of Rochester in the United States calculated the optical field distributions corresponding to different angular modes m (Literature 2). Dr. Xiankai Sun and Professor A. Yariv at the California Institute of Technology in the United States carried out modeling analysis and theoretical calculations on an annular DFB structure, a disk-shaped Bragg structure, and a circular microcavity Bragg structure (Literature 3).

[0003] The PCSEL adopts a double-lattice structure, and uses the phase difference between small circular holes and elliptical holes to partially cancel the optical field intensity and weaken the in-plane feedback. The annular grating structure can reduce the in-plane feedback by adjusting the duty cycle of the grating to be close to 0.5. However, both of these two structures are optimized and adjusted for the patterns.

[0004] Prior Art Documents

[0005] Literature 1: Takuya Inoue, Masahiro Yoshida, John Gelleta, et al., General recipe to realize photonic-crystal surface-emitting lasers with 100-W-to-1-kW single-mode operation, Nature Communications, Vol. 13, 2022.

[0006] Document 2: Pamela L. Greene, Radiation from Circular-Grating DistributedFeedback Lasers[D], University of Rochester, 2000.

[0007] Document 3: Xiankai Sun, Supermode Si / III-V Lasers and Circular BraggLasers[D], California Institute of Technology, 2010. Summary of the Invention

[0008] Based on this, the present invention aims to provide an improved diffractive surface-emitting semiconductor laser and its manufacturing method to solve at least one of the following problems.

[0009] In a first aspect, the present application provides a diffractive surface-emitting semiconductor laser, including an upper cladding layer, an upper waveguide layer, an active layer, a lower waveguide layer, and a lower cladding layer. When carriers are injected into the active layer, the active layer emits light. The diffractive surface-emitting semiconductor laser further includes:

[0010] A complementary optical modulation layer located in one or more of the upper cladding layer, the upper waveguide layer, the lower waveguide layer, and the lower cladding layer;

[0011] The complementary optical modulation layer includes an upper optical modulation layer and a lower optical modulation layer;

[0012] The lower optical modulation layer includes a first optical modulation material with a first refractive index and a second optical modulation material with a second refractive index. The first refractive index is different from the second refractive index, and the second optical modulation material is distributed in the first optical modulation material to form a high-low refractive index difference;

[0013] The upper optical modulation layer includes a third optical modulation material with a third refractive index and a fourth optical modulation material with a fourth refractive index. The third refractive index is different from the fourth refractive index, and the third optical modulation material is distributed in the fourth optical modulation material to form a high-low refractive index difference;

[0014] In the direction perpendicular to the laser output surface, the region where the second optical modulation material is located corresponds to the region where the fourth optical modulation material is located, and the region where the first optical modulation material is located corresponds to the region where the third optical modulation material is located.

[0015] The above-mentioned diffractive surface-emitting semiconductor laser uses a spatially complementary double-layer optical modulation layer to partially cancel the feedback intensity in the x-y plane, thereby further reducing the in-plane feedback intensity, which is beneficial for the device to achieve single-mode output in large areas. And through the epitaxial process, a low-refractive-index material is grown simultaneously within the double-layer optical modulation layer and on the waveguide / cladding surface, and then the substrate material is grown. In this way, the interface defects of the double-layer optical modulation layer are relatively low, which can reduce non-radiative recombination. This structure and process are also applicable to setting the double-layer optical modulation layer in the waveguide layer to improve the regulation of the optical field.

[0016] In one embodiment, the lower optical modulation layer is a first photonic crystal layer or a first grating layer, and the upper optical modulation layer is a second photonic crystal layer or a second grating layer.

[0017] In one embodiment, when the second optical modulation material and the fourth optical modulation material are low-refractive-index materials, the first optical modulation material and the third optical modulation material are high-refractive-index materials; when the second optical modulation material and the fourth optical modulation material are high-refractive-index materials, the first optical modulation material and the third optical modulation material are low-refractive-index materials.

[0018] In one embodiment, the first optical modulation material and the fourth optical modulation material are the same material; the second optical modulation material and the third optical modulation material are the same material.

[0019] In one embodiment, a waveguide layer or a cladding layer is further provided between the upper optical modulation layer and the lower optical modulation layer.

[0020] In one embodiment, the upper optical modulation layer and the lower optical modulation layer have equal thicknesses.

[0021] In one embodiment, the upper optical modulation layer and the lower optical modulation layer are located in the upper waveguide layer or the lower waveguide layer; the upper cladding layer, the upper waveguide layer, the active layer, the lower waveguide layer, and the lower cladding layer form an epitaxial layer; there is a first-order mode in the z-direction optical field perpendicular to the epitaxial layer.

[0022] In one embodiment, the emission wavelength of the laser is λ, the effective refractive index of the first-order mode is n, and the period a = λ / n; the active layer is within the range of ±a of a wave crest of the first-order mode of the z-direction optical field.

[0023] In one embodiment, the upper optical modulation layer and the lower optical modulation layer are within the range of ±a of another wave crest of the first-order mode of the z-direction optical field.

[0024] In one embodiment, the thicknesses of the upper optical modulation layer and the lower optical modulation layer do not exceed 0.5a.

[0025] In one embodiment, the distance between the upper optical modulation layer and the lower optical modulation layer does not exceed 0.7a.

[0026] In one embodiment, it further includes an electron blocking layer. The diffractive surface-emitting semiconductor laser is formed with a structure of a lower cladding layer, a lower waveguide layer, an active layer, a first upper waveguide layer, an electron blocking layer, a second upper waveguide layer, the lower optical modulation layer, a third upper waveguide layer, the upper optical modulation layer, a fourth upper waveguide layer, and an upper cladding layer from bottom to top.

[0027] In one embodiment, the electron blocking layer is within the range of ±0.35a of the node of the first-order mode of the light field in the z direction.

[0028] In a second aspect, the present application provides a method for manufacturing a diffractive surface-emitting semiconductor laser. The manufacturing method uses an epitaxial growth process to grow an n-type cladding layer, an n-type waveguide layer, a quantum well, a first p-type waveguide layer, an electron blocking layer, and a second p-type waveguide layer layer by layer. It is characterized in that the method further includes: forming a photonic crystal air hole or grating groove structure on the second p-type waveguide layer through a patterning and etching process; epitaxially growing a low-refractive-index or high-refractive-index material in the air hole or groove structure and on the second p-type waveguide layer; and continuously epitaxially growing a p-type waveguide layer and a p-type cladding layer.

[0029] In the above manufacturing method, by generating a complementary double-layer photonic crystal or grating structure, the feedback intensity in the x-y plane is partially offset, so that the in-plane feedback intensity can be further reduced, which is beneficial to the device to achieve single-mode output in a large area.

[0030] In a third aspect, the present application provides a method for manufacturing a diffractive surface-emitting semiconductor laser. The manufacturing method uses an epitaxial growth process to grow an n-type cladding layer and a third n-type waveguide layer layer by layer. The method further includes: forming a photonic crystal air hole or grating groove structure on the third n-type waveguide layer through a patterning and etching process; epitaxially growing a low-refractive-index or high-refractive-index material in the air hole or groove structure and on the third n-type waveguide layer; and continuously epitaxially growing an n-type waveguide layer, a quantum well, a p-type waveguide layer, and a p-type cladding layer.

[0031] In the above manufacturing method, by generating a complementary double-layer photonic crystal or grating structure, the feedback intensity in the x-y plane is partially offset, so that the in-plane feedback intensity can be further reduced, which is beneficial to the device to achieve single-mode output in a large area.

[0032] In one embodiment, after growing the p-type waveguide layer, the method further includes: growing an electron blocking layer; and finally growing a p-type cladding layer. Description of the Drawings

[0033] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in this specification. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0034] Figure 1 It is a schematic cross-sectional view of the structure of a diffractive surface-emitting semiconductor laser according to an embodiment of the present application;

[0035] Figure 2 It is a schematic cross-sectional view of the structure of a diffractive surface-emitting semiconductor laser according to another embodiment of the present application;

[0036] Figure 3 It is a schematic cross-sectional view of the structure of a diffractive surface-emitting semiconductor laser according to still another embodiment of the present application

[0037] Figure 4(a) shows Figure 3 the fundamental mode optical field distribution in the z direction of a GaN-based laser using the

[0038] Figure 4(b) shows Figure 3 the first-order mode optical field distribution in the z direction of a GaN-based laser using the

[0039] Figure 5(a) shows the relationship between the thickness of the third upper waveguide layer 43 and the emission coefficient in Example 3;

[0040] Figure 5(b) shows the diffracted light intensity distribution in the z direction of the lower optical modulation layer 7 and the upper optical modulation layer 9 when the emission coefficient in Example 3 is the largest;

[0041] Figure 5(c) shows the diffracted light intensity distribution in the z direction of the lower optical modulation layer 7 and the upper optical modulation layer 9 when the emission coefficient in Example 3 is the smallest;

[0042] Figure 6 shows the relationship between the emission coefficient and the third upper waveguide layer 43 in Example 4;

[0043] Figure 7 shows the optical field distribution in the z direction of the PCSEL structure in Comparative Example 2. Specific embodiments

[0044] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following provides a detailed description of the specific embodiments of the present invention with reference to the accompanying drawings. A lot of specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0045] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0046] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0047] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only implementation.

[0048] The PCSEL adopts a double-lattice structure to reduce the in-plane feedback, and the ring grating structure adjusts the in-plane feedback by changing the grating duty cycle. These two methods not only have limited ability to weaken the feedback, but also are sensitive to the size and structure of the photonic crystal / grating, and the uniformity of the pattern will also affect the final effect.

[0049] Based on the above problems, an embodiment of the present application provides a diffractive surface-emitting semiconductor laser. By adopting a double-layer photonic crystal or grating structure that is complementary in space, the feedback intensity in the x-y plane is partially cancelled out, thereby further reducing the in-plane feedback intensity and facilitating single-mode output of the device in the case of a large area. And through the epitaxial process, a low-refractive-index material layer is grown simultaneously in the air holes of the photonic crystal or the grating grooves and on the waveguide / cladding surface, and then the substrate material is grown. In this way, the interface defect of the double-layer photonic crystal or grating structure is relatively low, and non-radiative recombination can be reduced. This structure and process are also applicable to setting the double-layer photonic crystal or grating structure in the waveguide layer to improve the regulation of the optical field.

[0050] As Figure 1 and Figure 2 shown, an embodiment of the present application provides a diffractive surface-emitting semiconductor laser 100, which includes, from top to bottom, an upper cladding 8, an upper waveguide layer 4, an active layer 3, a lower waveguide layer 2, and a lower cladding 1. When carriers are injected into the active layer 3, the active layer 3 emits light. The diffractive surface-emitting semiconductor laser 100 further includes: a complementary optical modulation layer located in one or more of the upper cladding 8, the upper waveguide layer 4, the lower waveguide layer 2, and the lower cladding 1.

[0051] Among them, the complementary optical modulation layer includes an upper optical modulation layer 9 and a lower optical modulation layer 7 that have a complementary relationship in space; the lower optical modulation layer 7 includes a first optical modulation material with a first refractive index and a second optical modulation material with a second refractive index. The first refractive index is different from the second refractive index, and the second optical modulation material forms a high-low refractive index difference with the first optical modulation material. Optionally, the second optical modulation material can be distributed in the first optical modulation material to form a structure with a high-low refractive index difference. The upper optical modulation layer 9 includes a third optical modulation material with a third refractive index and a fourth optical modulation material with a fourth refractive index. The third refractive index is different from the fourth refractive index, and the third optical modulation material forms a high-low refractive index difference with the fourth optical modulation material. Optionally, the third optical modulation material can be distributed in the fourth optical modulation material to form a structure with a high-low refractive index difference. In the direction perpendicular to the laser output surface, the region where the second optical modulation material is located corresponds to the region where the fourth optical modulation material is located, and the region where the first optical modulation material is located corresponds to the region where the third optical modulation material is located.

[0052] Exemplarily, when the second optical modulation material and the fourth optical modulation material are low-refractive-index materials, the first optical modulation material and the third optical modulation material are high-refractive-index materials; when the second optical modulation material and the fourth optical modulation material are high-refractive-index materials, the first optical modulation material and the third optical modulation material are low-refractive-index materials.

[0053] In some embodiments, referring to Figures 1 to 3, the lower optical modulation layer 7 is a first photonic crystal layer or a first grating layer, and the upper optical modulation layer 9 is a second photonic crystal layer or a second grating layer. Optionally, the lower optical modulation layer 7 and the upper optical modulation layer 9 can be arranged in the following form: the surrounding material (corresponding to the first optical modulation material) of the lower optical modulation layer 7 is the surrounded material (corresponding to the third optical material) of the upper optical modulation layer 9, and the surrounded material (corresponding to the second optical modulation material) of the lower optical modulation layer 7 is the surrounding material (corresponding to the fourth optical modulation material) of the upper optical modulation layer 9, so as to realize the complementary relationship of the materials of the lower optical modulation layer 7 and the upper optical modulation layer 9 in the spatial position, and further make the feedback intensity in the xy plane partially offset, so as to reduce the in-plane feedback. Optionally, the photonic crystal can be an array-type photonic crystal or a ring-shaped photonic crystal; the grating can be a ring-shaped grating.

[0054] Exemplarily, the upper cladding can be an n-type cladding or a p-type cladding, and correspondingly, the lower cladding is a p-type cladding or an n-type cladding. The upper waveguide layer can be an n-type waveguide layer or a p-type waveguide layer, and correspondingly, the lower waveguide layer is a p-type waveguide layer or an n-type waveguide layer.

[0055] In some embodiments, as Figure 1 shown, the upper optical modulation layer 9 can be arranged in the upper cladding 8, for example, the upper optical modulation layer 9 can be arranged between the first upper cladding 81 and the second upper cladding 82.

[0056] In some embodiments, the lower optical modulation layer 7 and the upper optical modulation layer 9 are located in the upper waveguide layer 4, or the lower optical modulation layer 7 and the upper optical modulation layer 9 are located in the lower waveguide layer 2, and there is a first-order mode in the z-direction optical field perpendicular to the epitaxial layer. As Figure 2 shown, the lower optical modulation layer 7 and the upper optical modulation layer 9 can be arranged in the upper waveguide layer 4. For example, the lower optical modulation layer 7 can be arranged between the first upper waveguide layer 41 and the third upper waveguide layer 43, and the upper optical modulation layer 9 can be arranged between the third upper waveguide layer 43 and the fourth upper waveguide layer 44. By changing the positions of the lower optical modulation layer 7 and the upper optical modulation layer 9 in the z-direction optical field, the in-plane feedback intensity can be adjusted to adapt to the device area.

[0057] In some embodiments, a waveguide layer or a cladding layer is further arranged between the lower optical modulation layer 7 and the upper optical modulation layer 9. As Figure 1 shown, a first upper cladding 81 is arranged between the lower optical modulation layer 7 and the upper optical modulation layer 9; or, as Figure 2 shown, a third upper waveguide layer 43 is arranged between the lower optical modulation layer 7 and the upper optical modulation layer 9. By controlling the thickness of the first upper cladding 81 or the third upper waveguide layer 43, the diffraction phase generated by the lower optical modulation layer 7 and the upper optical modulation layer 9 can be adjusted, so as to facilitate the in-phase superposition of the two to obtain the maximum vertical emission coefficient.

[0058] In some embodiments, the emission wavelength of the laser is λ, the effective refractive index of the first-order mode is n, the period a = λ / n, and the active layer is within the range of ±a of a wave crest of the first-order mode of the optical field in the z direction. For example, it can be located at positions such as ±a, ±0.8a, ±0.6a, ±0.4a, ±0.2a, etc. of a wave crest. By making the lower optical modulation layer 7 and the upper optical modulation layer 9 near a wave crest of the first-order mode, it is beneficial to obtain a larger vertical emission coefficient.

[0059] When the lower optical modulation layer 7 and the upper optical modulation layer 9 are on one side of a wave crest of the optical field distribution in the z direction (it can be the fundamental mode, the first-order mode, or a higher-order mode), part of the feedback intensity is cancelled, and a larger in-plane feedback intensity is obtained; when the lower optical modulation layer 7 and the upper optical modulation layer 9 are on both sides of a wave crest of the first-order mode or a higher-order mode in the z direction, the in-plane feedback intensities generated by the two layers are close, the cancellation effect is significant, and the in-plane feedback intensity is low. Preferably, the thicknesses of the lower optical modulation layer 7 and the upper optical modulation layer 9 are equal.

[0060] Optionally, the lower optical modulation layer 7 and the upper optical modulation layer 9 are within the range of ±a of a wave crest of the first-order mode of the optical field in the z direction. For example, it can be located at positions such as ±a, ±0.8a, ±0.6a, ±0.4a, ±0.2a, etc. of another wave crest. With such a setting, it is beneficial to obtain a larger vertical emission coefficient.

[0061] Optionally, according to Figure 6 it can be known that in order to obtain a maximum value, the thicknesses of the lower optical modulation layer 7 and the upper optical modulation layer 9 do not exceed 0.5a. For example, they can be 0.5a, 0.4a, 0.3a, 0.2a, 0.1a, etc. Optionally, according to Figure 5(a), in order to obtain a point near the maximum value, the distance between the lower optical modulation layer 7 and the upper optical modulation layer 9 does not exceed 0.7a. For example, it can be 0.7a, 0.6a, 0.5a, 0.4a, 0.3a, 0.2a, 0.1a, etc.

[0062] In some embodiments, the diffractive surface-emitting semiconductor laser further includes an electron blocking layer (EBL layer) 5, and a structure of a lower cladding layer 1, a lower waveguide layer 2, an active layer 3, a first upper waveguide layer 41, an electron blocking layer 5, a second upper waveguide layer 42, a lower optical modulation layer 7, a third upper waveguide layer 43, an upper optical modulation layer 9, a fourth upper waveguide layer 44, and an upper cladding layer 8 is formed from bottom to top. By using the first-order mode or higher-order modes of the optical field in the z direction, the electron blocking layer 5 is inserted into the upper waveguide layer 4 and placed near the node of the optical field, which is beneficial to reducing the non-radiative loss brought by this layer and improving the electron-hole recombination rate at the same time. Optionally, the electron blocking layer 5 is within the range of ±0.35a of the node of the first-order mode of the optical field in the z direction, and can be located at positions such as ±0.35a, ±0.3a, ±0.2a, ±0.1a of the node, for example. Since the refractive index of the cladding layer material is lower than that of the waveguide layer material, the optical field can be mostly confined in the waveguide layer (propagating in the xy plane), that is, the optical field intensity in the z direction is mostly distributed in the waveguide layer. Therefore, by regulating the refractive index and thickness of the cladding layer and waveguide layer materials, it is beneficial to make the optical field in the z direction be the first-order mode and the electron blocking layer 5 be near the node of this first-order mode.

[0063] The embodiment of the present application also provides a preparation method of a diffractive surface-emitting semiconductor laser. This preparation method uses an epitaxial growth process to grow an n-type cladding layer, an n-type waveguide layer, a quantum well, a first p-type waveguide layer, an electron blocking layer, and a second p-type waveguide layer layer by layer. This preparation method further includes: forming a photonic crystal air hole or grating groove structure on the second p-type waveguide layer through a patterning and etching process; epitaxially growing a low-refractive-index or high-refractive-index material in the air hole or groove structure and on the second p-type waveguide layer; and continuously epitaxially growing a p-type waveguide layer and a p-type cladding layer.

[0064] The embodiment of the present application also provides a preparation method of a diffractive surface-emitting semiconductor laser. This preparation method uses an epitaxial growth process to grow an n-type cladding layer and a third n-type waveguide layer layer by layer. This preparation method further includes: forming a photonic crystal air hole or grating groove structure on the third n-type waveguide layer through a patterning and etching process; epitaxially growing a low-refractive-index or high-refractive-index material in the air hole or groove structure and on the third n-type waveguide layer; and continuously epitaxially growing an n-type waveguide layer, a quantum well, a p-type waveguide layer, and a p-type cladding layer.

[0065] In some embodiments, after growing the p-type waveguide layer, this preparation method further includes: growing an electron blocking layer; and finally growing a p-type cladding layer.

[0066] Next, the composition and effects of the diffractive surface-emitting semiconductor lasers in the foregoing embodiments will be further elaborated through several embodiments and comparative examples.

[0067] Embodiment 1

[0068] Taking a GaN-based semiconductor laser as an example, Figure 1 In the structure shown, a double grating structure is provided in the upper cladding 8. The first grating layer 7 is p-GaN surrounding ITO, the first upper cladding 81 is p-GaN, and the second grating layer 9 is ITO surrounding p-GaN. The absolute value of the in-plane feedback coefficient calculated is: 4.56×10 -5 .

[0069] Comparative Example 1

[0070] Based on Example 1, the first upper cladding 81 and the second grating layer 9 in the Figure 1 structure are removed. The absolute value of the in-plane feedback coefficient calculated is: 3.45×10 -4 .

[0071] In Comparative Example 1, the grating layer is only p-GaN surrounding ITO of the first grating layer 7, and the formed high and low refractive index difference generates in-plane feedback. While in Example 1, the ITO surrounding p-GaN of the second grating layer 9 is added, and its material structure is opposite to that of the first grating layer 7, and the in-plane feedback phase generated is different by π, partially canceling the in-plane feedback generated by the first grating layer 7. Therefore, the absolute value of the in-plane feedback coefficient is closer to 0.

[0072] Example 2

[0073] Figure 2 The optical field distribution in the z direction of the structure shown is similar to that of the Figure 3 structure shown. Considering that the waveguide layer 4 in the Figure 2 structure is relatively thick, in order to improve the recombination rate of electrons and holes in the active layer 3, an electron blocking layer (EBL layer) can be added in the region near the active layer 3 to form the Figure 3 structure shown. Since the EBL layer is heavily doped, it will cause non-radiative recombination. Therefore, the EBL layer is placed near the node of the first-order mode in the z direction. In this way, the EBL layer can be placed in the waveguide layer, which is different from the traditional structure (the EBL layer is in the cladding).

[0074] Using the Figure 3 structure shown, taking a 435nm GaN-based semiconductor laser as an example, under the same epitaxial structure, the optical field distributions of the fundamental mode and the first-order mode in the z direction are calculated, as shown in Figures 4(a) and 4(b). Since the thickness of the waveguide layer (upper waveguide layer + active layer + lower waveguide layer) is greater than 1μm, there is a first-order mode or higher-order modes. As shown in Figure 4(a), the highly doped EBL layer is located near the wave peak, increasing the fundamental mode loss. While in the first-order mode (Figure 4(b)), the EBL layer is at the node and does not significantly increase the device loss. After calculation, when the EBL layer is 20nm, the device loss Г EBL ≈0.07%; when the EBL layer is 60nm, Г EBL≈0.56%; when the EBL layer is 120 nm, Г EBL ≈2.20%. Calculate the effective refractive index of the first-order mode of this structure. The wavelength of the 435 nm light wave in the material is approximately 174 mn (i.e., the period a). Then, when the EBL layer is 120 nm, it is equivalent to approximately 0.7 times the period a. Correspondingly, when the EBL layer is 60 nm, it is equivalent to 0.34a; when the EBL layer is 20 nm, it is equivalent to 0.11a.

[0075] Example 3

[0076] Adopt Figure 3 the structure shown. The lower optical modulation layer 7 and the upper optical modulation layer 9 are set to 40 nm. By changing the thickness of the third upper waveguide layer 43, the phase of the diffracted light of the lower optical modulation layer 7 and the upper optical modulation layer 9 can be regulated, and then the output coefficient can be controlled and changed. The relationship between the thickness of the third upper waveguide layer 43 and the output coefficient is shown in Fig. 5(a). When the thickness of the third upper waveguide layer 43 is 72 nm, the output coefficient is the largest. At this time, the intensity distribution of the diffracted light of the lower optical modulation layer 7 and the upper optical modulation layer 9 in the z direction is shown in Fig. 5(b). When the thickness of the third upper waveguide layer 43 is 136 nm, the output coefficient is the smallest. At this time, the intensity distribution of the diffracted light of the lower optical modulation layer 7 and the upper optical modulation layer 9 in the z direction is shown in Fig. 5(c). Considering the actual process, preferably, the thickness of the third upper waveguide layer 43 or the first upper cladding layer 81 does not exceed 120 nm, that is, equivalent to 0.7 times the period a.

[0077] Example 4

[0078] Adopt Figure 3 the structure shown. When the lower optical modulation layer 7 and the upper optical modulation layer 9 are set to 40 nm, 70 nm, and 90 nm respectively, calculate the output coefficients corresponding to different thicknesses of the third upper waveguide layer 43, as Figure 6 shown. When the thickness of the third upper waveguide layer 43 is too large, in the calculated structure, it is greater than 90 nm. When the thickness of the third upper waveguide layer 43 is less than 100 nm, there is no maximum value. Therefore, the thickness of the third upper waveguide layer 43 or the first upper cladding layer 81 should be less than a certain value to obtain the maximum output coefficient. Considering the actual process, preferably, the thicknesses of the lower optical modulation layer 7 and the upper optical modulation layer 9 do not exceed 90 nm, that is, equivalent to 0.5 times the period a.

[0079] It is also deduced from Fig. 4(b) that the active layer 3 should be located within ±174 nm of a wave peak of the first-order mode, that is, the active layer is within the range of ±a of a wave peak of the first-order mode; the lower optical modulation layer 7 and the upper optical modulation layer 9 should be located within ±174 nm of another wave peak of the first-order mode, that is, within the range of ±a of another wave peak of the first-order mode.

[0080] Example 5

[0081] Refer toFigure 3 For the structure shown, when the lower cladding 1 is an n-type material and the upper cladding 8 is a p-type material, the process steps are as follows:

[0082] Using an epitaxial growth process, grow an n-type cladding, an n-type waveguide layer, a quantum well, a first p-type waveguide layer, an EBL layer, and a second p-type waveguide layer layer by layer. Through patterning and etching processes, form a photonic crystal air hole or grating groove structure on the second p-type waveguide layer. Then, grow a material with a lower refractive index and a higher bandgap width to a certain thickness. On the one hand, partially fill the photonic crystal air hole or grating groove with this lower refractive index material, and on the other hand, also grow this lower refractive index material in the unetched area of the second p-type waveguide layer. Next, continue to grow a p-type waveguide layer with a certain thickness, and the material is the same as that of the second p-type waveguide layer. Finally, grow a p-cladding.

[0083] Example 6

[0084] Reference Figure 2 For the structure shown, when the lower cladding 1 is a p-type material and the upper cladding 8 is an n-type material, the process steps are as follows:

[0085] Using an epitaxial growth process, grow an n-cladding and a third n-waveguide layer layer by layer. Through patterning and etching processes, form a photonic crystal air hole or grating groove structure on the third n-waveguide layer. Then, grow a material with a lower refractive index and a higher bandgap width to a certain thickness. On the one hand, partially fill the photonic crystal air hole or grating groove with this lower refractive index material, and on the other hand, also grow this lower refractive index material in the unetched area of the third n-waveguide layer. Next, continue to grow an n-type waveguide layer, a quantum well, a p-type waveguide layer, an EBL layer, and a p-cladding to a certain thickness.

[0086] Comparative Example 2

[0087] According to the GaAs-based PCSEL structure disclosed in Document 1, with a period of about 280 nm, calculate the distribution of the fundamental mode of the optical field in the z direction, as shown in Figure 7 shown. In the z direction, it is the fundamental mode, and the total thickness of the waveguide layer is about 300 nm, which is about one period. As can be seen from Figure 7 it, on the one hand, the thickness of the waveguide layer is relatively thin, which requires precise control of the growth of each layer of material. In addition, the photonic crystal layer is in the cladding, and its confinement factor is relatively large, resulting in relatively large losses and affecting the device efficiency.

[0088] It should be noted that the numbers representing quantities or properties used to describe and claim certain embodiments of the present application should be understood to be modified by the terms "substantially", "about", "approximate" or "essentially" in certain cases. For example, unless otherwise stated, "substantially", "about", "approximate" or "essentially" can indicate a ±20% variation of the value they describe. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, and such approximate values can vary according to the characteristics required by individual embodiments. In some embodiments, the numerical parameters should consider the specified significant digits and adopt the method of retaining the general number of digits. Although the numerical ranges and parameters used to confirm the breadth of the scope in some embodiments of the present application are approximate values, in specific embodiments, such numerical settings are as precise as possible within the feasible range.

[0089] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the various technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0090] The above-described embodiments merely represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A diffraction-type surface-emitting semiconductor laser, comprising, from top to bottom, an upper cladding layer, an upper waveguide layer, an active layer, a lower waveguide layer, and a lower cladding layer, wherein when carriers are injected into the active layer, the active layer emits light, characterized in that: The diffraction type surface emitting semiconductor laser further comprises: A complementary optical modulation layer, located in one or more of the upper cladding layer, the upper waveguide layer, the lower waveguide layer, and the lower cladding layer; The complementary optical modulation layer comprises an upper optical modulation layer and a lower optical modulation layer; The lower optical modulation layer includes a first optical modulation material having a first refractive index and a second optical modulation material having a second refractive index, the first refractive index is different from the second refractive index, and the second optical modulation material forms a high-low refractive index difference with the first optical modulation material; The upper optical modulation layer includes a third optical modulation material having a third refractive index and a fourth optical modulation material having a fourth refractive index, the third refractive index is different from the fourth refractive index, and the third optical modulation material and the fourth optical modulation material form a high-low refractive index difference; In a direction perpendicular to the laser emitting surface, the area where the second optical modulation material is located corresponds to the area where the fourth optical modulation material is located, and the area where the first optical modulation material is located corresponds to the area where the third optical modulation material is located; When the first optical modulation material and the fourth optical modulation material are low-refractive materials, the second optical modulation material and the third optical modulation material are high-refractive materials; when the first optical modulation material and the fourth optical modulation material are high-refractive materials, the second optical modulation material and the third optical modulation material are low-refractive materials.

2. The diffraction type surface emitting semiconductor laser according to claim 1, characterized in that: The lower optical modulation layer is a first photonic crystal layer or a first grating layer, and the upper optical modulation layer is a second photonic crystal layer or a second grating layer.

3. The diffraction type surface emitting semiconductor laser according to claim 1, characterized in that: The first optical modulation material and the fourth optical modulation material are the same material; the second optical modulation material and the third optical modulation material are the same material.

4. The diffraction type surface emitting semiconductor laser according to any one of claims 1 to 3, characterized in that: A waveguide layer or a cladding layer is further arranged between the upper optical modulation layer and the lower optical modulation layer.

5. The diffraction type surface emitting semiconductor laser according to any one of claims 1 to 3, characterized in that: The upper optical modulation layer and the lower optical modulation layer have the same thickness.

6. The diffraction type surface emitting semiconductor laser according to any one of claims 1 to 3, characterized in that: The upper optical modulation layer and the lower optical modulation layer are located in the upper waveguide layer or the lower waveguide layer; the upper cladding layer, the upper waveguide layer, the active layer, the lower waveguide layer, and the lower cladding layer constitute an epitaxial layer; There is a first-order mode in the z-direction optical field perpendicular to the epitaxial layer.

7. The diffraction type surface emitting semiconductor laser according to claim 6, characterized in that: The emission wavelength of the laser is λ, the effective refractive index of the first-order mode is n, and the period a=λ / n; the active layer is located within the range of ±a of a wave peak of the first-order mode of the light field in the z direction.

8. The diffraction type surface emitting semiconductor laser according to claim 7, characterized in that: The upper optical modulation layer and the lower optical modulation layer are located within a range of ±a of another peak of the first-order mode of the light field in the z direction.

9. The diffraction type surface emitting semiconductor laser according to claim 8, characterized in that: The thickness of the upper optical modulation layer and the lower optical modulation layer does not exceed 0.5a.

10. The diffraction type surface emitting semiconductor laser according to claim 8 or 9, characterized in that: The distance between the upper optical modulation layer and the lower optical modulation layer does not exceed 0.7a.

11. The diffraction type surface emitting semiconductor laser according to claim 6, characterized in that: It also includes an electron blocking layer. The diffraction-type surface emitting semiconductor laser forms a structure of a lower cladding layer, a lower waveguide layer, an active layer, a first upper waveguide layer, an electron blocking layer, a second upper waveguide layer, the lower optical modulation layer, a third upper waveguide layer, the upper optical modulation layer, a fourth upper waveguide layer, and an upper cladding layer from bottom to top.

12. The diffraction type surface emitting semiconductor laser according to claim 11, characterized in that: The electron blocking layer is located within the range of ±0.35a of the node of the first-order mode of the light field in the z direction.

13. A method for preparing a diffraction-type surface emitting semiconductor laser according to any one of claims 1 to 12, wherein the method adopts an epitaxial growth process to grow an n-type cladding layer, an n-type waveguide layer, a quantum well, a first p-type waveguide layer, an electron blocking layer, and a second p-type waveguide layer layer by layer, characterized in that: The method further comprises: Forming a photonic crystal hole or grating groove structure on the second p-type waveguide layer through patterning and etching processes; epitaxially growing a low refractive index or high refractive index material so that the empty hole or groove structure is partially filled with the low refractive index or high refractive index material, and forming the low refractive index or high refractive index material in the unetched region of the second p-type waveguide layer; Continue to epitaxially grow the p-type waveguide layer and the p-type cladding layer.

14. A method for preparing a diffraction-type surface emitting semiconductor laser according to any one of claims 1 to 12, wherein the method adopts an epitaxial growth process to grow an n-type cladding layer and a third n-type waveguide layer layer by layer, and the method further comprises: Forming a photonic crystal hole or grating groove structure on the third n-type waveguide layer through patterning and etching processes; epitaxially growing a low refractive index or high refractive index material so that the empty hole or groove structure is partially filled with the low refractive index or high refractive index material, and forming the low refractive index or high refractive index material in the region where the third n-type waveguide layer is not etched; Continue to epitaxially grow the n-type waveguide layer, quantum well, p-type waveguide layer, and p-type cladding layer.

15. The preparation method according to claim 14, characterized in that: After growing the p-type waveguide layer, the method further comprises: growing an electron blocking layer; Finally, the p-type cladding layer is grown.

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